In the refining of crude oils the heavy cuts including residue often are subjected to catalytic hydroprocessing to remove such components as sulfur, nitrogen, metals (e.g., nickel or vanadium, or both), and Conradson carbon through desulfurization, denitrogenation, demetallization, or asphaltene conversion or any combination thereof. Various types of heterogeneous hydroprocessing catalysts are used to promote these reactions by contacting the catalyst with feedstock under conditions of elevated temperature and pressure and in the presence of hydrogen.
A number of hydroprocessing catalysts have been described in the past to improve the hydroprocessing of heavy feedstocks. These include, e.g., U.S. Pat. No. 6,030,915 (de Boer) and U.S. Pat. No. 6,127,299 (de Boer et al.) which disclose grinding and mixing of waste catalyst particles to form new catalysts for hydroprocessing of heavy hydrocarbons.
Another hydroprocessing catalyst is disclosed in U.S. Pat. No. 7,824,541 (Bhan) that is particularly useful in the treatment of distillate feedstocks to manufacture low-sulfur distillate products. This catalyst is a co-mulled mixture of molybdenum trioxide, a Group VIII metal compound, and an inorganic oxide material. The co-mulled mixture is calcined. The molybdenum content of the catalyst is in the range of from 10.5 to 33 wt. %, calculated as an oxide. If the Group VIII metal component is nickel, it is present in the catalyst in the range of from 3.8 to 15.3 wt. %, calculated as an oxide. The catalyst also has a mean pore diameter that is in a specific and narrow range of from 50 to 100 angstroms. There is less than 4.5 percent of the total pore volume that is contained in its macropores having pore diameters greater than 350 angstroms and less than 1 percent of the total pore volume contained in its macropores having pore diameters greater than 1000 angstroms.
Disclosed in U.S. Pat. No. 7,820,036 (Bhan) is a catalyst useful in the hydroprocessing of a heavy hydrocarbon feedstock wherein the catalyst comprises a calcined mixture made by calcining a formed particle of a mixture comprising molybdenum trioxide, a nickel compound, and an inorganic oxide material. The catalyst may be made by mixing an inorganic oxide material, molybdenum trioxide, and a nickel compound to form a mixture that is formed into a particle and calcined to provide a calcined mixture. The process involves the hydrodesulfurization and hydroconversion of a heavy hydrocarbon feedstock which process may include the conversion of a portion of the pitch content of the heavy hydrocarbon feedstock and the yielding of a treated product having an enhanced stability as reflected by its P-value. The catalyst is made by a method comprising co-mulling an inorganic oxide material, molybdenum trioxide, and a nickel compound to form a mixture; forming said mixture into a particle; and calcining said particle to provide a calcined mixture having a pore size distribution such that at least 70% of the total pore volume of said calcined mixture is in the pores of said calcined mixture having a pore diameter in the range of from 70 Å to 150 Å.
Disclosed in U.S. Pat. No. 7,871,513 (Bhan) is a catalyst that is useful in the hydroprocessing of heavy hydrocarbon feedstocks. This catalyst is a calcined mixture made by calcining a formed particle of a mixture comprising molybdenum trioxide, a nickel compound, and an inorganic oxide material. The molybdenum content of the catalyst is in the range upwardly to 18 wt. %, calculated as an oxide. The nickel content of the catalyst is in the range upwardly to 5.1 wt. %, calculated as an oxide. The molybdenum source used in the preparation of the catalyst is in the form of molybdenum trioxide that is in a finely divided state.
While the aforementioned catalysts have been shown to have good hydroprocessing activity, there are continuing efforts to find new or improved catalyst compositions having increased catalytic activity or improved stability, or both. Any improvement in catalyst activity can result in the lowering of required reactor temperatures in order to obtain a product of a given nitrogen, sulfur, asphaltene, or metal content from a feedstock that is contaminated with these components. The lower reactor temperatures provide for energy savings and will extend the life of a catalyst. There also are ongoing efforts to find more economical methods of manufacturing the catalyst compositions.
Heavy hydrocarbon feedstocks such as vacuum tower bottoms and resides are typically more difficult to hydrotreat to remove such components as sulfur, nitrogen, metals and carbon than the lighter distillate and naphtha feedstocks. Specially designed catalysts that are different from those used for treating the lighter hydrocarbon feedstocks can be required in order to more economically treat the heavier hydrocarbon feedstocks. So, there is an ongoing need to find new or improve catalyst compositions that have good properties for the hydroprocessing of heavy hydrocarbon feedstocks.
It is, therefore, desirable to provide an improved hydroprocessing catalyst having good catalytic activity and stability and which can be economical to manufacture. One particular desire is to provide a hydroprocessing catalyst that is particularly useful in the hydroprocessing of heavy hydrocarbon feedstocks, and, especially such feedstocks that have exceptionally high sulfur and metals, e.g., nickel and vanadium, concentrations.